Field of the Invention
The present invention relates to a metal oxide semiconductor structure, especially to a metal oxide semiconductor structure having an opaque resin layer and at least two passivation layers.
Description of the Related Art
As IGZO (In—Ga—Zn—O) thin film transistor—utilizing IGZO for channel material—can be easily deposited on a glass substrate, many displays have utilized IGZO thin film transistors for controlling the gray levels of pixels. Please refer to FIG. 1, which illustrates a sectional view of a prior art thin film transistor structure. As illustrated in FIG. 1, the thin film transistor structure 100 includes a glass substrate 101, a gate electrode 102, a gate insulation layer 103, an IGZO layer 104, a source electrode 105a, a drain electrode 105b, a passivation layer 106, and a resin layer 107.
In the structure, the glass substrate 101 is used for carrying the other compositions of the thin film transistor structure.
The gate electrode 102, made of metal and deposited on the glass substrate 101, is used for coupling to a gate driving signal.
The gate insulation layer 103, being an insulation layer deposited over the gate electrode 102 and the glass substrate 101, is used to insulate the gate electrode 102 from the IGZO layer 104, the source electrode 105a, and the drain electrode 105b. 
The IGZO layer 104, being an N type semiconductor layer deposited on the gate insulation layer 103, functions as a channel.
The source electrode 105a, made of metal and deposited at one side of the IGZO layer 104, is used for coupling to a source driving signal.
The drain electrode 105b, made of metal and deposited at another side of the IGZO layer 104, is used for coupling to a pixel electrode.
The passivation layer 106, made of a silicon compound and deposited over the source electrode 105a, the IGZO layer 104, and the drain electrode 105b, is used for reducing leakage current of the channel.
The resin layer 107, being a transparent resin layer deposited over the source electrode 105a, the passivation layer 106, and the drain electrode 105b, is used to form a protection layer.
However, the thin film transistor structure specified above still suffers from photo leakage current effect. As illustrated in FIG. 2, the leakage current caused by a fourth light intensity—a strong light, with the thin film transistor being in a bias condition of Vgs=0V and Vds=15V, is around 0.1 mA. In addition, the thin film transistor structure also suffers from degradation caused by invasion of moisture, oxygen, or hydrogen—whose amount increases with time, and the degradation will further increase the leakage current. As illustrated in FIG. 3, in same test condition, the leakage current measured on a first date (June 22) is around 10−13 A, while the leakage current measured on a second date (July 15)—23 days later—is around 10−6 A.
To conquer the flaws of the prior art thin film transistor structure mentioned above, the present invention proposes a novel metal oxide semiconductor structure, which utilizes a better shielding design for preventing light, moisture, and air from reaching the channel, thereby reducing the photo leakage current and avoiding the degradation of the channel.